1. Field of the Disclosure
This disclosure generally relates to a human interface system and, more particularly, to an optical distance measurement system and operation method thereof having the function of detecting physiological characteristics of a user.
2. Description of the Related Art
Conventional optical distance measurement systems utilize a light sensor, such as a proximity sensor or an ambient light sensor to detect the intensity variation of ambient light so as to detect a relative distance and control the operation of an electronic device, e.g. temporarily turning ON/OFF a specific function, according to the relative distance. Presently, the optical distance measurement system has been widely applied to various electronic devices such as cell phones, tablet personal computers and personal digital assistants. With the development of industry, users spend more and more time on utilizing various portable electronic devices that puts a lot of stress on their bodies. However, conventional optical distance measurement systems are not able to detect the current physiological status of the user.
Conventional pulse oximeters utilize a noninvasive method to monitor the blood oxygenation and the heart rate of a user. A conventional pulse oximeter generally emits a red light beam (wavelength of about 660 nm) and an infrared light beam (wavelength of about 910 nm) to penetrate a part of the human body and detects an intensity variation of the penetrating light based on the feature that the oxyhemoglobin and the deoxyhemoglobin have different absorptivities in particular spectrum, e.g. referring to U.S. Pat. No. 7,072,701 and entitled “Method for spectrophotometric blood oxygenation monitoring”. After the intensity variation of the penetrating light of the two wavelengths is detected, the blood oxygenation can be calculated according to equation (1):Oxygen saturation=100%×[HbO2]/([HbO2]+[Hb])   (1)
wherein [HbO2] is an oxyhemoglobin concentration; and [Hb] is a deoxy-hemoglobin concentration.
Generally, the intensity variation of the penetrating light of the two wavelengths detected by a pulse oximeter is similar to FIG. 1. This is because blood vessels will expand and contract with heartbeats such that the blood volume that the light beams pass through will change to accordingly change the ratio of light energy being absorbed. Therefore, the absorptivity of blood of different light spectra can be calculated according to the intensity information changing continuously so as to calculate the physiology information such as the oxyhemoglobin and deoxyhemoglobin concentration, respectively. Finally, the blood oxygenation can be calculated according to equation (1).
However, as conventional pulse oximeters detect the intensity variation of the penetrating light, different intensity signals will be detected by detecting different parts of the human body. In addition, when the part of the human body being detected has a movement, a disturbed signal can be detected such that it is not possible to calculate correct physiology information. Therefore, conventional pulse oximeters cannot be applied to electronic devices operated in a moving state.
Accordingly, the present disclosure provides an optical distance measurement system and an operation method of the optical distance measurement system capable of detecting physiological characteristics of a user configured to detect a finger distance, a finger motion and physiological characteristics, wherein the signal noise caused by the finger movement can be eliminated in detecting the physiological characteristics.